Control of air pollution is a serious concern. Industrial plants and power plants often utilize combustion processes, such as in the treatment of chemical waste streams or in the generation of power. These combustion processes generally include nitric oxide (NO) as a combustion by-product. Nitric oxide and other nitrogen-containing emissions are generally undesirable as contributors to “acid rain.”
Gas streams from combustion processes are often scrubbed, i.e., contacted with water, to remove many of their contaminants. However, effective removal of nitric oxide from a gas stream is complicated by its low water solubility. To increase the effectiveness of a water scrubber system, it is necessary to oxidize the nitric oxide to nitrogen dioxide (NO2).
Nitric oxide does slowly oxidize in air to form nitrogen dioxide, one step in the manufacture of nitric acid from the combustion of ammonia. However, to make the oxidation of nitric oxide effective at low concentrations, some oxidizer more effective than air is required to increase the rate of reaction, such as ozone, or atomic oxygen. In fact, these materials have been used for this purpose. The problem with these materials is their high cost and complexity.
For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative methods and apparatus for removing nitric oxide from gaseous streams.